The relationship between haemoglobin concentrations and obstructive sleep apnea syndrome: A systematic review and meta-analysis.

This systematic review and meta-analysis investigates the relationship between haemoglobin (Hb) concentrations and obstructive sleep apnea syndrome (OSAS). Following PRISMA guidelines, we searched PubMed, EMBASE, and Cochrane Library from inception to March 8, 2024. Eligible studies included cross-sectional, cohort, and case-control designs comparing Hb concentrations in OSAS patients and healthy controls. Two reviewers independently screened records and extracted data. The risk of bias was assessed using the Joanna Briggs Institute checklist. A total of 27 studies involving 6499 OSAS subjects and 5199 controls were included. Hb concentrations were significantly higher in OSAS patients compared to controls (SMD: 0.28; 95 % CI: 0.18 to 0.39; I2 = 84.4 %). Subgroup analysis by OSAS severity showed that severe OSAS patients had higher Hb concentrations than those with mild/moderate OSAS. Sensitivity analyses confirmed the robustness of the findings. However, 7 studies reported opposite results, indicating possible regional or methodological differences. Hb concentrations are elevated in OSAS patients, with higher levels observed in severe cases. The significant heterogeneity and the predominance of studies from Turkey highlight the need for further research in diverse populations. Limitations include potential publication bias and variability in study designs. • A systematic review and meta-analysis were conducted to investigate the relationship between Hb concentrations and OSAS. • A total of 27 studies with 6499 OSAS patients and 5199 controls were included. • Hb concentrations were significantly higher in OSAS compared to CTRL (SMD: 0.28; 95 % CI: 0.18 to 0.39; I2 = 84.4 %). • The results suggest that elevated Hb levels in OSAS patients may reflect an adaptive response to intermittent hypoxia. • The relationship between OSAS severity and Hb concentrations highlights the potential clinical significance. [ABSTRACT FROM AUTHOR]